Tunable cavity resonator magnetron



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TUNABLE CAVITY RESONATOR MAGNETRON Filed. Aug. i3. 1947 E f Camel: L. Caccia ward the closed end walls of the resonators whereas the capacitive component of the field is distributed near the ends facing the cathode electrode. The capacitive portions of the resonators are also tied together by means of straps 8 and il.

The structure above described is used in many multi-cavity type magnetrons. No detailed illustration is believed necessary of these structural features inasmuch as the invention herein described pertains to the tuning mechanism which isv adaptable to magnetrons of all types having the basic construction outlined.

Adjacent the anode 4 there is supported a conducting plate 9 provided with a circular opening of such diameter that, when concentrically aligned with the resonators, it covers a substantial portion of each resonator near the closed end wall thereof. In other words, the conducting plate adjacent the resonators forms a conductive shield over the predominantly inductive portion of each resonator. The plate 9 is hinged at one end to the anode by means of hinge elements I9 and is attached at the other end to a collar I 2 on a rod I3 which extends through the envelope header I4 and terminates in a bushing l5. The plate 9 is also provided with apertures to admit the insulating bushings I 6 and I'I which hold the assembly for the cathode and the magnetic inserts I8 in place supported by the anode 4. The latter is supported on the header I4 in a conventional manner. An envelope cover I4 is secured vacuum tight to the header I4 at its periphery. i

The bushing I is secured to the header or base I4 by means o1' a iiexible bellows-type housing I9 which permits movement of the rod I3 with respect to the base I4 without disturbing the sealing of the inside structure and the evacuation of the envelope 20. Movement of the rod in the direction toward the anode 4 or away from it is effected by means of a differential screw 2! which is supported in a block 22 attached to the base I 4. The head 23 of the screw ZI is threaded in the block 22 and the threaded portion 24 of the screw 2| is similarly engaged with the block I5, as shown in Fig. 3. This type of construction permits a Vernier adjustment whereby several turns of the head 23 result in small increments of movement of the screw 2 I.

Other elements of the magnetron not shown in detail consist of the output coupling loop brought out through a coaxial line 26 provided with a seal 21. Similarly, the filament heating conductors of the cathode are brought out to the tubular shield 28 provided with a seal 29.

The operation of the tuning device herein described is based on the change of intercoupling between the resonators in that an obstruction is placed to the magnetic lines of force connecting adjacent resonators. lAs pointed out above the magnetic lines representing the inductive portion of the resonators, that is, the inductance, are predominantly near the end wall in each resonator. A conductive ring adjacent the peripheral edges of each resonator will therefore disturb the magnetic circuit. The plate 9 by its properly dimensioned aperture places a conductive shield near the peripheral edge of each resonator simultaneously and in its manner changes the effective inmovement of the plate 9 is eiected in a simple manner by displacing the rod I3 with respect to the base or header I4. In certain smaller magnetron structures the iiexibility of the base I4, which is only a thin metal plate, is sufficient to allow the slight motion required to actuate the plate 9. In such cases the bellows type housing I9 may be entirely omitted and the rod I3 may be welded directly to the base I4. However, in larger constructions it is preferable to rely on the additional ilexibility which the housing I9 provides. In a practical embodiment it was found that this tuning arrangement enabled a frequency change amounting to three percent of the operating frequency without significant decrease in tube performance.

While we have indicated the preferred embodiments of our invention of which we are now aware and have also indicated only one specic application for which our invention may be employed, it will be apparent that our invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims.

' We claim:

1. An electron discharge device including an anode electrode having a plurality of anode segments deiining a central space and a plurality of radially extending cavity resonators surrounding said space, a cathode electrode adjacent said anode electrode for supplying electrons to said central space, an envelope enclosing said electrodes, means for changing the electical characteristics of said resonators comprising a tuning element, hinge means mounting said tuning element on said anode electrode for pivotal movement of said tuning element relative to said resonators, actuating means independent of said hinge means connected to said tuning element within said envelope and extending therefrom, and adjustable means attached to said device and said element for moving said element.

2. An electron discharge device comprising a cathode electrode, an anode electrode surrounding said cathode electrode having a plurality oi' cavity resonators, an evacuated housing enclosing said electrodes, means for changing the electrical characteristics of said resonators comprising a tuning element adjacent said anode, hinge means mounting one end of said tuning element on said anode element for pivotal movement of said tuning element toward 'and away from said resonators, actuating means connected to the other end of said tuning element within said housing and extending therefrom, and adjustable means attached to said device and said actuating means for moving said actuating means.

3. An electron discharge device comprising a cathode electrode, an anode electrode surrounding said cathode electrode and having a plurality of intercoupled cavity resonators radially extending from said cathode, an envelope enclosing said electrodes, means for changing the electrical characteristics of said resonators comprising a tuning element controlling said intercoupling adjacent said anode, hinge means mounting said tuning element on said anode electrode for pivotal movement of said tuning element relative to said resonators, actuating means independent of said hinge means connected to said tuning element within said envelope and extending therefrom, and adjustable means attached to said device and said actuating means for moving said actuating means.

4. An electron discharge device comprising a cathode electrode, an anode electrode surrounding said cathode electrode and having a plurality of intercoupled cavity resonators radially extending from said cathode each forming a sector of a circle and terminating at the periphery thereof, an evacuated envelope enclosing said electrodes, means for changing the electrical characteristios of said resonators comprising a tuning element adjacent said anode, hinge means mounting one end of said tuning element on said anode element for pivotal movement of said tuning element toward and away from said resonators to change the effective peripheral termination of said resonators simultaneously in a degree varying with the distance of said tuning element from said anode, adjustable actuating means for said tuning element within said envelope and extending therefrom, and means attached to said device and said actuating means for moving said actuating means.

5. An electron discharge device including an anode electrode having a plurality of inter-coupled cavity resonators, a cathode adjacent said anode electrode for supplying electrons to said anode electrode, an evacuated envelope enclosing said electrode and said cathode, means for changing the electrical characteristics of said resonators and including a tuning element adjacent one end of said anode electrode and movable toward and from said resonators, said tuning element including a plate element hingedly mounted at one end to said anode electrode, an actuating member rigidly connected to the other' end of said tuning element and extending from said envelope, and adjustable means for adjusting said actuating member for pivoting said tuning element toward and from said anode electrode for tuning said device comprising a block attached to said member, a second block attached to said envelope and a differential screw threaded into said blocks.

JOHN S. DONAL, JR.

BARREMORE B. BROWN.

CARMEN L. CUCCIA.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,408,234 Spencer Sept. 24, 1946 2,408,237 Spencer Sept. 24, 1946 2,418,469 Hagstrum Apr. 8, 1947 2,422,465 Bondley June 17, 1947 2,424,496 Nelson July 22, 1947 

